The objective of this project is to investigate the hormonal mechanisms that are responsible for linear growth. Principal areas of investigation include improving the accuracy of the methods employed to diagnose growth hormone deficiency. We are also studying the effects of growth hormone and sex steroid administration on linear growth in patients with Turner's syndrome and delayed puberty. We are determining the cortisol production rate in normal children and adolescents. In addition, we are studying the mechanism of catch up growth in a primate model. We are determining the cortisol production rate and metabolic clearance rate in normal children and adolescents. We are studying the hormonal regulation of transcriptional expression of the growth hormone receptor gene. In addition, we are examining the effect of inducing pubertal delay in children with extreme short stature, in order to prolong prepubertal growth prior to the pubertal spurt and possibly enhance ultimate height by delaying epiphyseal fusion. We are also investigating the effects of growth hormone therapy on the adult height of non-growth-hormone deficient children with short stature through a randomized, double-blind, placebo-controlled clinical trial. In addition, we are investigating the growth hormone secretory dynamics in patients with hypophosphatemic rickets. Finally, we are studying the effects of growth hormone-releasing factor on linear growth in growth hormone-deficient children by using different treatment regimens in order to optimize growth.